1. Technical Field
The present invention relates to a projector.
2. Related Art
A projector which includes a light source, a light modulation device for modulating light emitted from the light source, and a projection device for expanding and projecting the modulated light is known. One of examples known as this type of projector has such a structure which includes a transmission type liquid crystal panel (transmission type light modulation device) and a pair of polarization plates between which the transmission type liquid crystal panel is disposed. The polarization plates are constituted by an entrance side polarization plate disposed on the light entrance side of the transmission type liquid crystal panel, and an exit side polarization plate disposed on the light exit side of the transmission type liquid crystal panel.
According to the projector thus constructed, the temperature of the interior of the projector is easily raised by heat generated from the entrance side and exit side polarization plates and the light modulation device having absorbed a part of light emitted from the light source device, for example. For solving this problem, a temperature measuring member for measuring the temperature of the periphery of the light modulation device is provided in the vicinity of the light modulation device so that temperature rise on the periphery of the light modulation device can be prevented by using a cooling fan disposed within the projector and supplying air based on temperature information obtained by the temperature measuring member (for example, see JP-A-2009-47824).
Moreover, a projector which includes a reflection type liquid crystal panel (reflection type light modulation device) is known (for example, see JP-A-2009-36819). According to the projector disclosed in JP-A-2009-36819, a wire grid (reflection type polarization plate) is disposed on the light entrance side of the reflection type liquid crystal panel in such a position as to be inclined to the reflection type liquid crystal panel. Polarized light having passed through the wire grid is reflected by the reflection type liquid crystal panel after modulation toward the wire grid, and again passes through the wire grid or is reflected by the wire grid toward the exit side, depending on the polarization direction of the polarized light. An exit side polarization plate is disposed on the optical path of the polarized light reflected toward the exit side in such a position as to be inclined to the wire grid. The reflection type liquid crystal panel, the wire grid, and the exit side polarization plate are fixed to an attachment member in such a manner as to produce a substantially sealed space between these components.
According to the projector shown in JP-A-2009-36819, however, the accurate temperature of the periphery of the light modulation device is difficult to be measured by using the temperature measuring member disposed between the reflection type liquid crystal panel and the wire grid, for example. In this case, temperature rise of the projector cannot be sufficiently prevented.
In case of the projector disclosed in JP-A-2009-36819, the temperature changes of the reflection type liquid crystal panel, the wire grid, and the exit side polarization plate in response to the change of input signals are different from one another. More specifically, the temperature changes of the wire grid and the exit side polarization plate are larger than the temperature change of the reflection type liquid crystal panel. Thus, the accurate temperature of the light modulation device is difficult to be determined based on the measurement of the peripheral temperature affected by the larger temperature changes of the wire grid and the exit side polarization plate.